Integrated chips are constructed using complex fabrication processes that form a plurality of different layers on top of one another. Many of the different layers are patterned using photolithography, a process by which a photosensitive material is selectively exposed to electromagnetic radiation. For example, photolithography may be used to define back-end-of-the-line metallization layers that are formed on top of one another.
To ensure that the different layers are formed with a good structural definition, the electromagnetic radiation must be properly focused. To properly focus electromagnetic radiation, a substrate must be substantially planar to avoid depth of focus problems. Chemical mechanical planarization (CMP) is a widely used process by which both chemical and mechanical forces are used to planarize a semiconductor substrate. The planarization prepares the substrate for the formation of a subsequent layer by providing a planar surface that mitigates depth of focus problems.